Question

Do I need to link to all DNS servers?

I have purchased a domain name from 123-reg, and I have set everything up to ensure my droplet links to the domain. This said, the domain provider only allows up to four DNS entries… The DigitalOcean takes up three. Whilst, 123-reg supplies to other nameservers. Essentially, it has broken my email service…, and I want to know how to go about this situation. Thank you in advance.